| From | Greg Kroah-Hartman <> | Subject | [PATCH 4.7 110/143] mm: silently skip readahead for DAX inodes | Date | Mon, 5 Sep 2016 18:44:46 +0200 |
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4.7-stable review patch. If anyone has any objections, please let me know.
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From: Ross Zwisler <ross.zwisler@linux.intel.com>
commit 11bd969fdefea3ac0cb9791224f1e09784e21e58 upstream.
For DAX inodes we need to be careful to never have page cache pages in the mapping->page_tree. This radix tree should be composed only of DAX exceptional entries and zero pages.
ltp's readahead02 test was triggering a warning because we were trying to insert a DAX exceptional entry but found that a page cache page had already been inserted into the tree. This page was being inserted into the radix tree in response to a readahead(2) call.
Readahead doesn't make sense for DAX inodes, but we don't want it to report a failure either. Instead, we just return success and don't do any work.
Link: http://lkml.kernel.org/r/20160824221429.21158-1-ross.zwisler@linux.intel.com Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com> Reported-by: Jeff Moyer <jmoyer@redhat.com> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Dave Chinner <david@fromorbit.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Jan Kara <jack@suse.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- mm/readahead.c | 9 +++++++++ 1 file changed, 9 insertions(+)
--- a/mm/readahead.c +++ b/mm/readahead.c @@ -8,6 +8,7 @@ */ #include <linux/kernel.h> +#include <linux/dax.h> #include <linux/gfp.h> #include <linux/export.h> #include <linux/blkdev.h> @@ -545,6 +546,14 @@ do_readahead(struct address_space *mappi if (!mapping || !mapping->a_ops) return -EINVAL; + /* + * Readahead doesn't make sense for DAX inodes, but we don't want it + * to report a failure either. Instead, we just return success and + * don't do any work. + */ + if (dax_mapping(mapping)) + return 0; + return force_page_cache_readahead(mapping, filp, index, nr); }
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